If he can use AM frequency broadcast, why hasn't he used other forms of radio communication to communicate with people out of state or for that matter, the rest of the world? Surely if 1% of the entire human population has survived then some of that 1% would have at least made the same attempt in doing so... which brings me to another point...

We know at the end of the movie, a survivor colony in Vermont exists, surely they would have made some attempt to broadcast their location or broadcast a message to any survivors.

When Neville washes his dog Sam, why is there running water? You would think after 3 years and since he's the only one alive in New York. All water treatment facility would be abandoned wouldn't it?

The deer hunt - Nevilles got food and stuff, there's really no reason why he needs to kill the deer now wouldn't it? Unless its for sport/entertainment and it seems like he's doing it in the movie for food. Another thing about the lion scene, you'd think the lions, being wild animals that they are, would attack Neville?!??

How is it that every night you hear howls outside his apartment and yet he lives undetected for past 3 years? You would think that some of those things would make SOME attempt entering the buildings at one point in time. The only logical explanation I can think of has something to do with whatever he's pouring outside his apartment.

Compound #6 worked on the rat or at least showed signs of improvements, so why did it not work on the dog? The same compound worked on the female vampire/zombie thing.

How did the woman & child get there? The bridges were blown up and the tunnels were probably flooded. Navigating by a boat? That's a little far-fetched

The attack scene - we can clearly see the Vampire/Zombie thing sink his teeth into Neville's neck/shoulder and fling him around like a ragdoll. Wouldn't that probably kill him or anyone for that matter?

Why did he need to sacrifice himself at the end? He's found the cure and there's enough room in the emergency hatch. Why not hide in the hatch, throw the grenade as the glass is about to break, close it and come out the next day?

Your explanation makes no sense. If he had survived till the next day, he could always move out in the daylight the next day and temporarily relocate elsewhere (if they can't find him for 3 years, they certainly won't have much luck finding him again if he relocated) in the city or better yet, leave the island like how Anna and the child got to the island in the first place. So why would he need to die at all?